Heat treatable coated article having zirconium nitride and ito based ir reflecting layers

ABSTRACT

Coated articles include two or more functional infrared (IR) reflecting layers optionally sandwiched between at least dielectric layers. The dielectric layers may be of or including silicon nitride or the like. At least one of the IR reflecting layers is of or including zirconium nitride (e.g., ZrN) and at least another of the IR reflecting layers is of or including indium-tin-oxide (ITO).

This invention relates to coated articles that include two or morefunctional infrared (IR) reflecting layers possibly sandwiched betweenat least dielectric layers, and/or a method of making the same. Inexample embodiments, at least one of the IR reflecting layers is of orincluding zirconium nitride (e.g., ZrN) and at least another of the IRreflecting layers is of or including indium-tin-oxide (ITO). The coatingmay be designed so that the coated articles realize one or more of:desirable glass side reflective visible coloration that is not too red(e.g., glass side reflective a* color value(s) from −14 to +1.6); adesirably low solar heat gain coefficient (SHGC); desirable visibletransmission (TY or T_(vis)); desirably low film side visiblereflectance; thermal stability upon optional heat treatment (HT) such asthermal tempering; desirably low normal emittance (E_(n)); and/ordesirably high light-to-solar gain ratio (LSG). Such coated articles maybe used in the context of monolithic windows, insulating glass (IG)window units, laminated windows, and/or other suitable applications.

BACKGROUND AND SUMMARY OF THE INVENTION

Low solar factor (SF) and solar heat gain coefficient (SHGC) values aredesired in some applications, particularly in warm weather climates.Solar factor (SF), calculated in accordance with EN standard 410,relates to a ratio between the total energy entering a room or the likethrough a glazing and the incident solar energy. Thus, it will beappreciated that lower SF values are indicative of good solar protectionagainst undesirable heating of rooms or the like protected bywindows/glazings. A low SF value is indicative of a coated article(e.g., IG window unit) that is capable of keeping a room fairly cool insummertime months during hot ambient conditions. Thus, low SF values aresometimes desirable in hot environments. High light-to-solar gain (LSG)values are also desirable. LSG is calculated as T_(vis)/SHGC. The higherthe LSG value, the more visible light that is transmitted and the lessamount of heat that is transmitted by the coated article. While low SFand SHGC values, and high LSG values, are sometimes desirable for coatedarticles such as IG window units and/or monolithic windows, theachievement of such values may come at the expense of sacrificingcoloration and/or reflectivity values. In particular, conventionalattempts to achieve low SHGC values have often resulted in undesirablylow LSG values and/or undesirable visible coloration of the coating. Itis often desirable, but difficult, to achieve a combination ofacceptable visible transmission (TY or T_(vis)), low emissivity,desirable glass side reflective coloration (e.g., desirable a* and b*glass side reflective color values), low SHGC, and high LSG for a coatedarticle in window applications, especially if it desired to use a glasssubstrate that is not deeply tinted.

SF (G-Factor; EN410-673 2011) and SHGC (NFRC-2001) values are calculatedfrom the full spectrum (T_(vis), Rg and Rf) and are typically measuredwith a spectrophotometer such as a Perkin Elmer 1050. The SFmeasurements are done on monolithic coated glass, and the calculatedvalues can be applied to monolithic, IG and laminated applications.

Silver based low-E (low emissivity) coatings for windows are known inthe art. However, silver is not particularly durable, and can be easilycorroded if exposed to moisture for instance. Thus, silver based low-Ecoatings are not desirable for monolithic applications such asmonolithic windows, and are typically used in IG window units includingmultiple glass panes, because of the durability problems of silver basedlow-E coatings.

Solar control coatings not based on silver are known, for example,having a layer stack of glass/Si₃N₄/NiCr/Si₃N₄/NiCr/Si₃N₄, where theNiCr layer may be nitrided. For example, see U.S. Patent Document2012/0177899 which is hereby incorporated herein by reference. Whilelayer stacks of U.S. Patent Document 2012/0177899 provide reasonablesolar control and are overall good coatings, they are lacking in certainrespects. The glass side reflective a* values (a* under R_(G)Y) inExamples 1, 4 and 5 in paragraphs 0025-0026 of US '899 are −17.8,−15.95, and +2.22, respectively. Examples 1 and 4 in US '899 areundesirable because the glass side reflective a* values are too negativeat −17.8 and −15.95, respectively. And when R_(G)Y is reduced down to15.82% in Example 5, this results in the glass side reflective a* colorvalue in Example 5 becoming too red with a value of +2.22. Thus, thecoatings described in US '899 were not able to achieve a combination ofacceptable visible reflectivity values and glass side reflective a*coloration values.

It would be desirable according to example embodiments of this inventionfor a coating to be designed so as to have a combination of acceptablevisible transmission (TY or T_(vis)), desirable glass side reflectivecoloration (e.g., desirable a* and/or b* reflective color values),desirably low film side visible reflectance, low emittance/emissivity,low SHGC, and high LSG for a coated article in window applications.

In certain example embodiments of this invention, certain applicationssuch as monolithic window applications desire glass side reflectivecoloration that is not significantly red. In other words, certainapplications such as monolithic window applications desire glass sidereflective a* color values that are either negative or no greater than+1.6 or +1.0 (glass side reflective a* values higher than +1.6 areundesirably red). Such reflective a* values are especially desirable forexample in the context of glass side reflective(R_(G[or outside, or exterior])Y) a* values.

Certain embodiments of this invention relate to coated articles thatinclude two or more functional infrared (IR) reflecting layers that maybe sandwiched between at least transparent dielectric layers, and/or amethod of making the same. The dielectric layers may be of or includesilicon nitride or the like. In certain example embodiments, at leastone of the IR reflecting layers is of or including zirconium nitride(e.g., ZrN) and at least another of the IR reflecting layers is of orincluding indium-tin-oxide (ITO). It has surprisingly and unexpectedlybeen found that the use of these different materials for the differentIR reflecting layers in a given solar control coating surprisinglyresults in improved optics such as improved glass side reflective a*values, low emittance, low film side visible reflectance, and/or highLSG values which are often desirable characteristics in windowapplications, and the provision of the IR reflecting layer of orincluding ITO allows coated articles to be more easily tailored fordesired visible transmission values while the IR reflecting layer of orincluding ZrN can keep the normal emissivity, SF and/or SHGC valuesreasonably low and improve durability. Coating according to embodimentsof this invention may be designed so that before and/or after anyoptional heat treatment such as thermal tempering the coated articlesrealize one or more of: desirable glass side reflective visiblecoloration that is not too red (e.g., reflective a* color value(s) from−14 to +1.6); a desirably low solar heat gain coefficient (SHGC);desirable visible transmission (TY or T_(vis)); desirably low film sidevisible reflectance; thermal stability upon optional heat treatment (HT)such as thermal tempering; desirably low normal emissivity/emittance(E_(n)); and/or desirably high light-to-solar gain ratio (LSG). Notethat SHGC may be as high as 80% for uncoated glass. The higher the LSGvalue, the greater the energy saving. Such coated articles may be usedin the context of monolithic windows, insulating glass (IG) windowunits, laminated windows, and/or other suitable applications.

In an example embodiment of this invention, there is provided a coatedarticle including a coating supported by a glass substrate, the coatingcomprising: a first infrared (IR) reflecting layer comprising ITO on theglass substrate; a first dielectric layer comprising silicon nitride onthe glass substrate over at least the first IR reflecting layercomprising ITO; a second layer IR reflecting layer comprising a nitrideof zirconium on the glass substrate over at least the first dielectriclayer comprising silicon nitride, so that the first dielectric layercomprising silicon nitride is located between at least the first IRreflecting layer comprising ITO and the second IR reflecting layercomprising the nitride of zirconium; a second dielectric layercomprising silicon nitride on the glass substrate over at least thesecond IR reflecting layer comprising the nitride of zirconium; whereinthe coating contains no IR reflecting layer based on silver; wherein thecoating has a normal emittance (E_(n)) value of no greater than 0.30;and wherein the coated article has: a visible transmission from about15-80%, a film side visible reflectance no greater than 15%, a SHGCvalue of no greater than 0.45, a glass side reflective a* value of from−14.0 to +1.6, and a light-to-solar gain ratio (LSG) of at least 1.10.

In an example embodiment of this invention, there is provided a coatedarticle including a coating supported by a glass substrate, the coatingcomprising: a first infrared (IR) reflecting layer comprising ITO on theglass substrate; a first dielectric layer comprising silicon nitride onthe glass substrate over at least the first IR reflecting layercomprising ITO; a second layer IR reflecting layer comprising a nitrideof zirconium on the glass substrate over at least the first dielectriclayer comprising silicon nitride, so that the first dielectric layercomprising silicon nitride is located between at least the first IRreflecting layer comprising ITO and the second IR reflecting layercomprising the nitride of zirconium; a second dielectric layercomprising silicon nitride on the glass substrate over at least thesecond IR reflecting layer comprising the nitride of zirconium; whereinthe coating contains no IR reflecting layer based on silver; wherein thecoating has a normal emittance (E_(n)) value of no greater than 0.30;and wherein the coated article has: a visible transmission from about15-80% and a light-to-solar gain ratio (LSG) of at least 1.17.

Thus, this invention covers monolithic window units, IG window units,laminated window units, and any other article including a glasssubstrate having a coating thereon as claimed. Note that monolithicmeasurements may be taken by removing a coated substrate from an IGwindow unit and/or laminated window unit, and then performing monolithicmeasurements. It is also noted that for a given coating the SF and SHGCvalues will be significantly higher for a monolithic window unit thanfor an IG window unit with the same coated article.

IN THE DRAWINGS

FIG. 1 is a partial cross sectional view of a monolithic coated article(heat treated or not heat treated) according to an example embodiment ofthis invention.

DETAILED DESCRIPTION OF CERTAIN EXAMPLE EMBODIMENTS OF THE INVENTION

Referring now more particularly to the accompanying drawings in whichlike reference numerals indicate like parts throughout the severalviews.

A coating 8 is designed so as to have a combination of acceptablevisible transmission (TY or T_(vis)), desirable glass side reflectivecoloration (e.g., desirable a* and b* reflective color values), low filmside visible reflectance, low emittance/emissivity, low SHGC, and highLSG for a coated article for use in window applications or the like. Asvisible transmission increases when the IR reflecting layer(s) becomethinner, parameters such as SHGC will also increase, and normalemittance/emissivity (E_(n)) will decrease, with this being based on thedesired transmission for instance of a given coated article for a givenapplication. Example applications include architectural windows,residential windows, monolithic windows, automotive windows, and/or IGwindows.

Certain embodiments of this invention relate to coated articles having acoating 8 on a glass substrate 1, where the coating includes two or morefunctional infrared (IR) reflecting layers 3 and 5 which may besandwiched between at least transparent dielectric layers 2, 4, 6, 7,and/or a method of making the same. Some of the transparent dielectriclayers, such as dielectric layer(s) 2 and/or 7, are optional and neednot be provided in certain example embodiments. The dielectric layers 2,4 and 6 may be of or include silicon nitride, silicon oxynitride, or thelike. Transparent dielectric overcoat 7, of or including zirconium oxideor any other suitable material, is optional. In certain exampleembodiments, at least one of the IR reflecting layers is of or includingzirconium nitride (e.g., ZrN) and at least another of the IR reflectinglayers is of or including ITO. In the FIG. 1 embodiment, upper IRreflecting layer 5 is of or including zirconium nitride (e.g., ZrN) andlower IR reflecting layer 3 is of or including ITO. It has surprisinglyand unexpectedly been found that the use of these different materialsfor the different IR reflecting layers 3 and 5 in a given solar controlcoating surprisingly results in improved optics such as improved glassside reflective a* values, low emittance, low film side visiblereflectance, and/or higher LSG values which are often desirablecharacteristics in window applications, and the provision of the IRreflecting 3 layer of or including ITO allows coated articles to be moreeasily tailored for desired visible transmission values and high LSGvalues while the IR reflecting layer of or including ZrN 5 provides fordesirably low normal emissivity and/or SHGC values for a given thicknessof IR reflecting material. Coating 8 according to embodiments of thisinvention may be designed so that before and/or after any optional heattreatment such as thermal tempering the coated articles realize one ormore of: desirable glass side reflective visible coloration that is nottoo red (e.g., reflective a* color value(s) from −14 to +1.6); adesirably low solar heat gain coefficient (SHGC); desirable visibletransmission (TY or T_(vis)); low film side reflectance; thermalstability upon optional heat treatment (HT) such as thermal tempering;desirably low E_(n); and/or a desirably high light-to-solar gain ratio(LSG). In example embodiments of this invention, the coating 8 containsno IR reflecting layer based on Ag or Au.

In certain example embodiments of this invention, certain applicationssuch as monolithic window applications desire glass side reflectivecoloration that is not significantly red. In other words, certainapplications such as monolithic window applications desire glass sidereflective a* color values that are either negative or no greater than+1.6 (glass side reflective a* values higher than +1.6 are undesirablyred). Such glass side reflective a* values are not too red and aredesirable in the context of glass side reflective (R_(G)Y) a* values.

Coated articles may optionally be heat treated in certain exampleembodiments of this invention, and are preferably designed to be heattreatable. The terms “heat treatment” and “heat treating” as used hereinmean heating the article to a temperature sufficient to achieve thermaltempering, heat bending, and/or heat strengthening of the glassinclusive article. This definition includes, for example, heating acoated article in an oven or furnace at a temperature of least about 580degrees C., more preferably at least about 600 degrees C., for asufficient period to allow tempering, bending, and/or heatstrengthening. In certain instances, the HT may be for at least about 4or 5 minutes. The coated article may or may not be heat treated indifferent embodiments of this invention.

FIG. 1 is a cross sectional view of a coated article according to anexample embodiment of this invention. In the FIG. 1 embodiment the solarcontrol coating 8 includes two IR reflecting layers 3 and 5, andtransparent dielectric layers 2, 4, 6 and 7. The coated article includesat least glass substrate 1 (e.g., clear, green, bronze, grey, blue, orblue-green glass substrate from about 1.0 to 12.0 mm thick, morepreferably from 4-8 mm thick, with an example glass substrate thicknessbeing 6 mm), transparent dielectric layers 2, 4, 6 (e.g., of orincluding silicon nitride [e.g., Si₃N₄], silicon oxynitride, siliconzirconium nitride, or some other suitable dielectric), and IR reflectinglayers 3, 5. Upper IR reflecting layer 5 is of or including zirconiumnitride (e.g., ZrN, preferably a stoichiometric or substantiallystoichiometric type) and lower IR reflecting layer 3 is of or includingconductive ITO. The upper IR reflecting layer 5 is of or includesZrN_(x) in certain example embodiments of this invention, where x ispreferably from 0.8 to 1.2, more preferably from 0.9 to 1.1, with anexample value being about 1.0. These “x” values provide forimproved/lowered emittance values compared to if “x” is too low forinstance. The zirconium nitride has been found to be very durablecompared to silver for example, and more resistant to moisture inducedcorrosion compared to silver for example. It has surprisingly andunexpectedly been found that the use of these different materials forthe different IR reflecting layers 3 and 5 in a given solar controlcoating provides for surprisingly results as explained herein. While theIR reflecting layer 5 may include some small amount of oxygen in certaininstances, it is preferable that layer 5 is substantially free of oxygensuch as no more than 8% oxygen, more preferably no more than about 5%oxygen, and most preferably no more than about 3% or 2% oxygen incertain embodiments (atomic %). The coated article may optionallyinclude transparent dielectric overcoat layer 7 of or including aprotective material such as zirconium oxide (e.g., ZrO₂) or siliconoxynitride. Optionally, a dielectric layer of or including siliconoxynitride and/or zirconium silicon oxynitride of any suitablestoichiometry may be located between and contacting layers 6 and 7 inthe upper part of the layer stack in certain example embodiments. Incertain example embodiments of this invention, coating 8 does notinclude any metallic IR blocking or reflecting layer of or based on Agor Au. In certain example embodiments of this invention, IR reflectinglayers 3 and 5 reflect at least some IR radiation, and do not contactany other metal or metal based IR reflecting layer. In certain exampleembodiments, it is possible for each of the layers to include othermaterials such as dopants. It will be appreciated of course that otherlayers may also be provided, or certain layers may be omitted, anddifferent materials may be used, in certain alternative embodiments ofthis invention.

The overall coating 8 of FIG. 1 includes at least the illustrated layersin certain example embodiments, with layers 2 and 7 in particular beingoptional. It is noted that the terms “oxide” and “nitride” as usedherein include various stoichiometries. For example, the term siliconnitride (for one or more of layers 2, 4, 6) includes stoichiometricSi₃N₄, as well as non-stoichiometric silicon nitride, and these layersmay be doped with other material(s) such as Al and/or O. The illustratedlayers may be deposited on glass substrate 1 via magnetron sputtering,any other type of sputtering, or via any other suitable technique indifferent embodiments of this invention. It is noted that other layer(s)may be provided in the stack shown in FIG. 1 such as between layers 2and 3, or between layers 3 and 4, or between the substrate 1 and layer2, or the like. Generally, other layer(s) may also be provided in otherlocations of the coating. Thus, while the coating 8 or layers thereofis/are “on” or “supported by” substrate 1 (directly or indirectly),other layer(s) may be provided therebetween. Thus, for example, thelayer system 8 and layers thereof shown in FIG. 1 are considered “on”the substrate 1 even when other layer(s) may be provided therebetween(i.e., the terms “on” and “supported by” as used herein are not limitedto directly contacting). However, there may be the direct contacts shownin FIG. 1 in preferred embodiments.

In certain example embodiments of this invention, dielectric layers 2,4, and 6 may each have an index of refraction “n” of from 1.7 to 2.7 (at550 nm), more preferably from 1.9 to 2.5 in certain embodiments, andmost preferably from about 2.0 to 2.06 in preferred embodiments of thisinvention. One, two, three, or all of these layers 2, 4, 6 may be of orinclude silicon nitride and/or silicon oxynitride in certain exampleembodiments of this invention. In such embodiments of this inventionwhere layers 2, 4, 6 comprise silicon nitride (e.g., Si₃N₄) or siliconoxynitride, sputtering targets including Si employed to form theselayers may or may not be admixed with up to 1-20% (e.g., 8%) by weightaluminum or stainless steel (e.g. SS#316), with about this amount thenappearing in the layers so formed. Even with this amount(s) of aluminumand/or stainless steel, such layers are still considered dielectriclayers. In certain example embodiments, each of the IR reflecting layers3 and 5 is provided between respective nitride layers (e.g., siliconnitride based layers 2, 4, 6) in order to reduce or prevent damage tothe IR reflecting layers during possible heat treatment (e.g., thermaltempering, heat bending, and/or heat strengthening) thereby permittingpredictable coloration to be achieved following the heat treatment atmultiple viewing angles. While FIG. 1 illustrates a coated articleaccording to an embodiment of this invention in monolithic form, coatedarticles according to other embodiments of this invention may compriseIG (insulating glass) window units or the like.

Turning back to the FIG. 1 embodiment, various thicknesses may be usedconsistent with one or more of the needs discussed herein. According tocertain example embodiments of this invention, example thicknesses (inangstroms) and materials for the respective layers of the FIG. 1embodiment on the glass substrate 1 are as follows in certain exampleembodiments for achieving desired transmission, glass side reflectivecoloration, low film side visible reflectance, low emittance, anddesirably low SHGC value(s) and/or a desirably high LSG value (layersare listed in order moving away from the glass substrate 1):

TABLE 1 (Thicknesses in FIG. 1 embodiment) Example Preferred ExampleLayer Range (Å) (Å) (Å) silicon nitride (layer 2):  20−500 Å  40−200 Å 50 Å IR reflector (e.g., ITO)  100−950 Å 300−800 Å 750 Å (layer 3):silicon nitride (layer 4): 150−1100 Å 200−450 Å 371 Å IR reflector(e.g., ZrN)  50−450 Å 130−300 Å 250 Å (layer 5): silicon nitride (layer6):  20−800 Å 300−550 Å 514 Å overcoat (e.g., ZrO₂)  10−150 Å  20−40 Å 30 Å (layer 7):

Table 1 above relates to, for example, embodiments where coating 8 isdesigned so that before and/or after any optional heat treatment such asthermal tempering the coated articles realize one, two, three, four,five, six or all of: desirable glass side reflective visible colorationsuch as not too red reflective color (e.g., reflective a* color value(s)from −14 to +1.6); a desirably low SHGC; desirable visible transmission;thermal stability upon optional HT such as thermal tempering; desirablylow E_(n); desirably low film side visible reflectance, and/or adesirably high LSG. In certain example embodiments, lower IR reflectinglayer 5 may be physically thicker than upper IR reflecting layer by atleast 50 angstroms (Å), more preferably by at least 100 Å, sometimes byat least 200 Å, and most preferably by at least 300 Å. In certainexample embodiments of this invention, upper dielectric layer 6 isphysically thicker than center dielectric layer 4 by at least 50angstroms (Å), more preferably by at least 100 Å.

Before and/or after any optional heat treatment (HT) such as thermaltempering, in certain example embodiments of this invention coatedarticles according to the FIG. 1 embodiment may have color/opticalcharacteristics as follows in Table 2 (measured monolithically). It isnoted that subscript “G” stands for glass side reflective, subscript “T”stands for transmissive, and subscript “F” stands for film sidereflective. As is known in the art, glass side (G) means when viewedfrom the glass side (as opposed to the layer/film side) of the coatedarticle. Film side (F) means when viewed from the side of the coatedarticle on which the coating is provided. The characteristics below inTable 2 are in accordance with Illuminant C, 2 degree Observer, and areapplicable to HT and non-HT coated articles herein. Glass sidereflective coloration may be such that coated articles appear neutralcolored, blue-green colored, or yellow-green colored in various exampleembodiments of this invention.

TABLE 2 Color/Optical Characteristics (FIG. 1 embodiment monolithic)General Preferred Most Preferred T_(vis) (TY): 15-80% 20-70% 30-60% (or35-45%) a*_(T) −10 to +5   −8 to +2  −6 to 0  b*_(T) −15 to +7   −10 to+3   −9 to +2 R_(G)Y(glass side): ≤40% ≤35% ≤30% a*_(G) −14 to +1.6 −10to +1.6 −8 to +1 b*_(G) −15 to +9   −9 to +4  −8 to +1 R_(F)Y(filmside): ≤15% ≤12% ≤10% a*_(F) −15 to +15  −11 to +11   −3 to +11 b*_(F)−25 to +9   −20 to +4   −16 to 0  E_(n): ≤0.30 ≤0.25 ≤0.22 SHGC: ≤0.45≤0.40 ≤0.33 LSG: ≥1.10 ≥1.17 ≥1.25

For purposes of example only, Example 1 representing an exampleembodiments of this invention, as well we Comparative Examples (CE) 1-5,are set forth below.

EXAMPLES

Comparative Examples (CEs) 1-4 and Example 1 were sputter-deposited (asall examples) layer stacks on clear glass substrates. And CE 5 was alayer stack modeled on a green glass substrate. The optical measurementsare monolithic measurements. Optical data for CEs 1-5 and Example 1 isin accordance with Illuminant C, 2 degree Observer. The silicon nitridelayers were doped with about 8% Al. The ZrN layers were approximatelystoichiometric. Layer thicknesses are in angstroms (Å). “L” in Table 4below stand for Layer (e.g., L2 means layer 2 shown in FIG. 1, L3 meanslayer 3 shown in FIG. 1, and so forth). It will be shown below that theuse of ITO for layer 3 and ZrN for layer 5 in Example 1 provided forunexpectedly improved optics compared to the use of TiN or NiCr forlayer 3, and TiN for layer 5, in CEs 1-5.

TABLE 3 Layer Stacks of Comparative Examples (CEs) 1-5 Example L2(Si₃N₄)L3(NiCr) or L3(TiN) L4(Si₃N₄) L5(TiN) L6(Si₃N₄) L7(ZrO₂) CE 1: 220 n/a240 670 310 10 40 CE 2: 140 n/a 200 590 240 30 40 CE 3: 40 n/a 180 350120 30 40 CE4: 50 68 n/a 723 268 171 30 CE5: 50 66 n/a 714 261 206 30

Measured monolithically after thermal tempering (HT), the CEs had thefollowing characteristics.

TABLE 4 Measured Monolithic Optical Data (CEs 1−5) Parameter CE 1 CE 2CE 3 CE4 CE5 T_(vis) (TY) 18.6% 24.2% 35.3% 23.1% 21.8% (transmission ):L*_(T): 50.2 56.3 66.0 55.2 53.8 a*_(T) −7.2 −7.0 −5.5 −3.15 −5.86b*_(T) −4.3 −1.5 −0.8 −8.27 −7.97 R_(G)Y  9.5%  9.2% 13.0% 12.0%  9.6%(glass side refl. %): L*_(G): 36.9 36.4 42.8 41.2 37.1 a*_(G): −3.2 −2.8−0.3 −0.8 −1.45 b*_(G): −3.5 0.4 −5.7 −1.8 −2.1 R_(F)Y 25.2% 19.1% 10.8%14.1% 11.2% (film side refl. %): L*_(F): 57.3 50.8 39.2 44.4 39.9a*_(F): 5.3 4.7 7.0 0.6 −0.3 b*_(F): −8.3 −6.1 −5.4 −4.9 −4.1 E_(n):0.18 0.25 0.36 0.25 0.25 SHGC (NFRC− 0.21 0.24 0.31 0.28 0.27 2001):LSG: 0.80 1.01 1.14 0.83 0.81

Example 1 according to an example of this invention had the followinglayer stack. Layer thicknesses are in angstroms (Å).

TABLE 5 Layer Stack of Example 1 Example L3(ITO) L4(Si₃N₄) L5(ZrN)L6(Si₃N₄) Ex. 1: 750 371 250 514

Measured monolithically, Example 1 had the following characteristics.

TABLE 6 Measured Monolithic Optical Data (Example 1) Parameter Example 1T_(vis) (TY)(transmission): 39.6% a*_(T) −3.01 b*_(T) +0.65 R_(G)Y(glassside refl. %): 28.9% a*_(G): −7.06 b*_(G): −5.9 R_(F)Y(film side refl.%):  9.5% a*_(F): +9.9 b*_(F): −14.8 E_(n): 0.197 SHGC (NFRC-2001): 0.31LSG: 1.30

It can be seen by comparing CEs 1-5 (Tables 3-4) with Example 1 (Tables5-6), that the use of ITO and ZrN in Example 1 for layers 3 and 5,respectively, provided for unexpected results. For instance, the LSGvalues of CEs 1, 2, 4 and 5 were all 1.01 or less, which is undesirable.And while the LSG of CE3 was 1.14, CE3 could not maintain a lowemittance as evidenced by its undesirably high normalemittance/emissivity (E_(n)) of 0.36, which means that insufficient IRis blocked by the coating of CE3. No comparative example (CE) has asufficiently low normal emittance/emissivity (E_(n)) combined withdesirably high LSG, desirably low SHGC, and desirably low film sidevisible reflectance.

The use of ITO for layer 3 and ZrN for layer 5 in Example 1 unexpectedlyallowed for a combination of high LSG, low SHGC, and lowemittance/emissivity (E_(n)), along with reduced film side visiblereflectance and glass side reflective coloration that was not too red.The LSG value of 1.30 means a significant energy saving.

In an example embodiment of this invention, there is provided a coatedarticle including a coating supported by a glass substrate, the coatingcomprising: a first infrared (IR) reflecting layer comprising ITO on theglass substrate; a first dielectric layer comprising silicon nitride onthe glass substrate over at least the first IR reflecting layercomprising ITO; a second layer IR reflecting layer comprising a nitrideof zirconium on the glass substrate over at least the first dielectriclayer comprising silicon nitride, so that the first dielectric layercomprising silicon nitride is located between at least the first IRreflecting layer comprising ITO and the second IR reflecting layercomprising the nitride of zirconium; a second dielectric layercomprising silicon nitride on the glass substrate over at least thesecond IR reflecting layer comprising the nitride of zirconium; whereinthe coating contains no IR reflecting layer based on silver; wherein thecoating has a normal emittance (E_(n)) value of no greater than 0.30;and wherein the coated article has: a visible transmission from about15-80%, a film side visible reflectance no greater than 15%, an SHGCvalue of no greater than 0.45, a glass side reflective a* value of from−14.0 to +1.6, and a light-to-solar gain ratio (LSG) of at least 1.10.

In the coated article of the immediately preceding paragraph, thecoating in some instances contains only two IR reflecting layers.

In the coated article of any of the preceding two paragraphs, the firstdielectric layer comprising silicon nitride may be located between anddirectly contacting the first and second IR reflecting layers.

In the coated article of any of the preceding three paragraphs, thesecond IR reflecting layer comprising the nitride of zirconium maycomprise ZrN_(x), where x is from 0.8 to 1.2, more preferably from 0.9to 1.1.

In the coated article of any of the preceding four paragraphs, thesecond IR reflecting layer may contain from 0-8% oxygen (atomic %), morepreferably from 0-5% oxygen (atomic %).

In the coated article of any of the preceding five paragraphs, thecoating may further comprise another dielectric layer comprising siliconnitride and/or silicon oxynitride located between and contacting theglass substrate and the first IR reflecting layer.

In the coated article of any of the preceding six paragraphs, the secondIR reflecting layer may consist essentially of the nitride of zirconium.

In the coated article of any of the preceding seven paragraphs, thecoating may further comprise an overcoat comprising an oxide ofzirconium.

In the coated article of any of the preceding eight paragraphs, thecoated article may have a visible transmission from about 20-70% (morepreferably from 30-60%, and most preferably from 35-45%) and/or alight-to-solar gain ratio (LSG) of at least 1.17.

In the coated article of any of the preceding nine paragraphs, thecoated article may have a light-to-solar gain ratio (LSG) of at least1.17, more preferably an LSG of at least 1.25.

In the coated article of any of the preceding ten paragraphs, the coatedarticle may have a film side visible reflectance no greater than 12%,more preferably no greater than 10%.

In the coated article of any of the preceding eleven paragraphs, theglass substrate may be a clear glass substrate, and may or may not beheat treated (e.g., thermally tempered).

In the coated article of any of the preceding twelve paragraphs, thecoated article may have a glass side reflective a* value of from −10 to+1.6, and/or a film side reflective a* value of from −15 to +15.

In the coated article of any of the preceding thirteen paragraphs, oneor more of the dielectric layers comprising silicon nitride may furthercomprise oxygen and/or may be doped with aluminum.

In the coated article of any of the preceding fourteen paragraphs, thecoated article may be a monolithic window.

In the coated article of any of the preceding fifteen paragraphs, thecoated article measured monolithically may have an SHGC value of nogreater than 0.40, more preferably no greater than 0.33.

In the coated article of any of the preceding sixteen paragraphs, thefirst IR reflecting layer comprising ITO may be from 100-950 Å thick,and/or the second IR reflecting layer comprising the nitride ofzirconium may be from 50-450 Å thick.

In the coated article of any of the preceding seventeen paragraphs, thefirst IR reflecting layer comprising ITO may be from 300-800 Å thick,and/or the second IR reflecting layer comprising the nitride ofzirconium may be from 130-300 Å thick.

In the coated article of any of the preceding eighteen paragraphs, thefirst IR reflecting layer comprising ITO may be physically thicker thanthe second IR reflecting layer comprising the nitride of zirconium by atleast 50 Å, more preferably by at least 100 Å, even more preferably byat least 200 Å, and most preferably by at least 300 Å.

Once given the above disclosure many other features, modifications andimprovements will become apparent to the skilled artisan. Such otherfeatures, modifications and improvements are therefore considered to bea part of this invention, the scope of which is to be determined by thefollowing claims:

1-33. (canceled)
 34. A coated article including a coating supported by aglass substrate, the coating comprising: a first dielectric layercomprising silicon nitride on the glass substrate; a first infrared (IR)reflecting layer comprising ITO on the glass substrate, wherein thefirst dielectric layer comprising silicon nitride is located between atleast the glass substrate and the first IR reflecting layer comprisingITO; a second dielectric layer comprising silicon nitride on the glasssubstrate over at least the first IR reflecting layer comprising ITO; asecond layer IR reflecting layer comprising a nitride of zirconium onthe glass substrate over at least the first and second dielectric layerscomprising silicon nitride, so that the second dielectric layercomprising silicon nitride is located between at least the first IRreflecting layer comprising ITO and the second IR reflecting layercomprising the nitride of zirconium; a third dielectric layer comprisingsilicon nitride on the glass substrate over at least the second IRreflecting layer comprising the nitride of zirconium; wherein thecoating contains no IR reflecting layer based on silver, and containsonly two IR reflecting layers; wherein the first IR reflecting layercomprising ITO is from 300-800 Å thick, and the second IR reflectinglayer comprising the nitride of zirconium is from 130-300 Å thick; andwherein the coated article has: a visible transmission from about15-80%, a film side visible reflectance no greater than 15%, an SHGCvalue of no greater than 0.45, and a glass side reflective a* value offrom −14.0 to +1.6.
 35. The coated article of claim 34, wherein thefirst dielectric layer comprising silicon nitride is located between anddirectly contacting the first and second IR reflecting layers.
 36. Thecoated article of claim 34, wherein the second IR reflecting layercomprising the nitride of zirconium comprises ZrN_(x), where x is from0.8 to 1.2.
 37. The coated article of claim 34, wherein the second IRreflecting layer contains from 0-8% oxygen (atomic %).
 38. The coatedarticle of claim 34, wherein the coating further comprises anotherdielectric layer comprising silicon nitride located between andcontacting the glass substrate and the first IR reflecting layer. 39.The coated article of claim 34, wherein the first dielectric layercomprising silicon nitride further comprises oxygen.
 40. The coatedarticle of claim 34, where the second IR reflecting layer consistsessentially of the nitride of zirconium.
 41. The coated article of claim34, wherein the coating further comprises an overcoat comprising anoxide of zirconium.
 42. The coated article of claim 34, wherein thecoated article has a film side visible reflectance no greater than 12%.43. The coated article of claim 34, wherein the coated article has afilm side visible reflectance no greater than 10%.
 44. The coatedarticle of claim 34, wherein the glass substrate is a clear glasssubstrate.
 45. The coated article of claim 34, wherein the first IRreflecting layer comprising ITO is physically thicker than the second IRreflecting layer comprising the nitride of zirconium by at least 100 Å.46. The coated article of claim 34, wherein the first IR reflectinglayer comprising ITO is physically thicker than the second IR reflectinglayer comprising the nitride of zirconium by at least 300 Å.
 47. Acoated article including a coating supported by a glass substrate, thecoating comprising: a first dielectric layer comprising silicon nitrideon the glass substrate; a first infrared (IR) reflecting layercomprising ITO on the glass substrate, wherein the first dielectriclayer comprising silicon nitride is located between at least the glasssubstrate and the first IR reflecting layer comprising ITO; a seconddielectric layer comprising silicon nitride on the glass substrate overat least the first IR reflecting layer comprising ITO; a second layer IRreflecting layer comprising a nitride of zirconium on the glasssubstrate over at least the first and second dielectric layerscomprising silicon nitride, so that the second dielectric layercomprising silicon nitride is located between and directly contactingthe first IR reflecting layer comprising ITO and the second IRreflecting layer comprising the nitride of zirconium; a third dielectriclayer comprising silicon nitride on the glass substrate over at leastthe second IR reflecting layer comprising the nitride of zirconium;wherein the coating contains no IR reflecting layer based on silver, andcontains only two IR reflecting layers; wherein the first IR reflectinglayer comprising ITO is from 300-800 Å thick, and the second IRreflecting layer comprising the nitride of zirconium is from 130-300 Åthick; and wherein the coated article has a visible transmission fromabout 15-80% and a light-to-solar gain ratio (LSG) of at least 1.17. 48.The coated article of claim 47, wherein the first IR reflecting layercomprising ITO is physically thicker than the second IR reflecting layercomprising the nitride of zirconium by at least 100 Å.
 49. The coatedarticle of claim 47, wherein the first IR reflecting layer comprisingITO is physically thicker than the second IR reflecting layer comprisingthe nitride of zirconium by at least 300 Å.